Passive heat transfer devices are of much interest in applications such as electronics cooling. Heat pipes are one such device which are commonly used. They are a liquid and vapor device in which liquid is pumped through capillarity from the condenser to the evaporator. The pumping effect in this device requires a wick, which produces a high pressure loss, limits the maximum heat transport distance and/or power that can be supported before dry-out occurs.
Another technology node that is useful is a thermosyphon, as shown in FIG. 1. In operation, liquid is vaporized in an evaporator 101. The vapor then travels through a vapor tube 102 to the condenser 100. Heat is removed from the condenser 100 causing the liquid 104 to accumulate at the bottom. The accumulated liquid 104 in the condenser 100 is driven by gravity through a liquid tube 103 back to the evaporator 101. The evaporators in these devices are typically pool boiling devices with an enhanced surface 105 that may consist of fins, a porous layer or even an etched surface. The maximum boiling heat transfer coefficient can be limited in this device because there are a finite amount of nucleation sites, and therefore, a limited length of solid/liquid/vapor contact, where the heat transfer rate is the highest.
In accordance with prior art, as represented in FIG. 1, the liquid tube 103 is routed at a lower elevation than the liquid 104 pool height inside the condenser 100. However, there are many situations that may arise that prevent the liquid tube 103 to be routed at a lower elevation. As shown in FIG. 2, there may be components 106 to avoid at a low elevation which require the liquid tube 103 to be routed above these components 106. In this situation, it is possible for all the liquid 104 in the system to be trapped on the condenser 100 side of the apex of the liquid tube 103. If this situation arises, the thermosyphon will experience a dry-out condition and cease to function properly.
There is a need, therefore for a thermosyphon in which the liquid can flow to the evaporator 101 under adverse conditions.